The long-term objective of this research is to describe the joint receptor system from the receptor level to the cortical level by an engineering systems approach. Improved clinical testing techniques and an increased knowledge of sensory neurophysiology are expected to result from these studies. In the near term the system will be examined from the joint receptor level to the thalamic level. Psychophysical experiments will test several hypotheses concerning the functions of the several types of receptors and serve as a bridge between our basic neurophysiological findings and the clinical neurological testing of receptor function that we propose. Passive kinesthesis is now believed to be dependent primarily on various receptors associated with the joints. We propose to study the static and dynamic response properties of the joint receptors and their central projections through the nervous system to the cortex. Engineering systems analysis will be used as a conceptual and operational tool in these studies. This characterization will form a conceptual basis for new clinical tests that offer the promise of more precise evaluation of neurological deficits and the location and evaluation of neuropathies.